Umts reselection performance in small cell systems

ABSTRACT

A beacon cell adapted for use in a small cell RAN includes dual identities—a beacon identity and a regular or “live” identity—in which the identities are individually configured to address differing performance requirements in the small cell RAN. The beacon identity in the cell is specially configured to meet the performance requirements for mobile user equipment (UE) to be able to quickly and easily move from a macrocell base station in a mobile operator&#39;s network to the small cell RAN using a process called “reselection.” The live identity is configured to meet all requirements for service to be provided to the UE within the small cell RAN. Once captured by the beacon identity of the beacon cell, the UE can then immediately reselect to the live identity of the cell which operates in a conventional manner.

BACKGROUND

Operators of mobile systems such as Universal Mobile TelecommunicationsSystems (UMTS) are increasingly relying on wireless small cell radioaccess networks (RANs) in order to deploy indoor voice and data servicesto enterprises and other customers. Such small cell RANs typicallyutilize multiple-access technologies capable of supportingcommunications with multiple users using radio frequency (RF) signalsand sharing available system resources such as bandwidth and transmitpower. While such small cell RANs operate satisfactorily in manyapplications, there exists a need for further improvements in small cellRAN technologies.

This Background is provided to introduce a brief context for the Summaryand Detailed Description that follow. This Background is not intended tobe an aid in determining the scope of the claimed subject matter nor beviewed as limiting the claimed subject matter to implementations thatsolve any or all of the disadvantages or problems presented above.

SUMMARY

A beacon cell adapted for use in a small cell RAN includes dualidentities—a beacon identity and a regular or “live” identity—in whichthe identities are individually configured to address differingrequirements in the small cell RAN. The beacon identity in the cell isspecially configured to meet the requirements for mobile user equipment(UE) such as mobile phones, smartphones, tablets, etc., to be able toquickly and easily move from a macrocell base station in a mobileoperator's network to the small cell RAN using a process called“reselection.” Reselection can be utilized, for example, when theequipment user moves from an outdoor area within the radio coverage ofthe macrocell into a building serviced by the small cell RAN. Once theUE is associated with the small cell RAN, the beacon identity is nolonger used to control the UE. Instead, the beacon cell internallyswitches the UE from the beacon identity to the live identity. The liveidentity is configured to meet all requirements for service to beprovided to the UE within the small cell RAN. Thus, the present beaconcell advantageously enables rapid reselection of a UE from the macrocellto the small cell RAN and then provides the same level of RAN service tothe UE in the small cell RAN as would a conventional small cell.

Due to the predetermined configuration of macrocells, reselectionrequires a reserved primary scrambling code (PSC) for cellidentification, termed a “magic PSC” in the description that follows.There are usually very few, for example six, magic PSCs available intypical applications. However, since reselection does not rely on celldisambiguation (as needed for other RAN services) a PSC in a beaconidentity can be reused without any risk of disambiguation failure. Inaddition, the beacon identity can be broadcast with reduced power andlower signal quality so long as the broadcast channels remain decodableover an acceptable fraction of the coverage area of the beacon cell. Bycontrast, the live identities of all cells in the small cell RAN cannottypically be satisfactorily configured using just the magic PSCs andthus they require other (i.e., non-magic) PSCs. The live identities thususe a relatively large set of PSCs and can operate at normal power andsignal quality levels to facilitate satisfactory quality-of-service andcell disambiguation for RAN service. The reduced power level of thebeacon identity reduces the opportunity for RF interference with thelive identity but still enables rapid reselection to the small cell RANfrom the macrocell. Once captured by the beacon identity of the beaconcell, the UE can then immediately reselect to the live identity of thecell which operates in a conventional manner including, for example,handover to neighboring cells in the small cell RAN as the UE movesthrough the service area.

In various illustrative examples, each deployed beacon cell isconfigured to reuse (i.e., commonly share) the same magic PSCs. As thenumber of magic PSCs that are reserved for reselection is strictlylimited, the present beacon cell advantageously broadens the footprintof cells in the small cell RAN that are equipped to capture UEs from themacrocell via reselection because many or all of the cells in a givendeployment can be beacon cells.

The beacon identity will typically broadcast only to the minimumrequirements for reselection by reconfiguring several physical andtransport channels in the downlink to the UE. Timing and powerutilization of the beacon cell are also manipulated to further optimizereselection performance. The beacon identity may also be adapted forselective and/or dynamically configurable operation using a duty cycle,for example, or be operated in response to conditions on the small cellRAN such as UE loading.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustrative mobile telecommunications environment inwhich the present small cell reselection performance improvement may bepracticed;

FIG. 2 shows how a primary scrambling code (PSC) is utilized to uniquelyidentify cells to user equipment (UE) where cells can include a servingcell and neighboring cells;

FIGS. 3 and 4 respectively show two different ways in which a servingcell may be changed;

FIG. 5 shows illustrative features and characteristics which areincorporated into a beacon cell which may be utilized to implement thepresent small cell reselection performance improvement;

FIG. 6 is an illustrative taxonomy of modifications that may be utilizedto implement aspects of beacon cell functionality;

FIG. 7 is a flowchart of an illustrative method for improved reselectionperformance using a beacon cell;

FIG. 8 illustratively shows how a small cell RAN (Radio Access Network)may include a mix of cell types;

FIG. 9 shows an illustrative radio interface protocol architecture (3GPPTS 25.301); and

FIG. 10 shows a simplified functional block diagram of illustrativehardware infrastructure for a radio node that may be utilized toimplement the present beacon cell.

Like reference numerals indicate like elements in the drawings. Elementsare not drawn to scale unless otherwise indicated.

DETAILED DESCRIPTION

FIG. 1 shows an illustrative mobile telecommunications environment 100in which the present small cell reselection performance improvement maybe practiced. The mobile telecommunications environment 100, in thisillustrative example, is arranged as a Universal MobileTelecommunications System (UMTS) as described by the Third GenerationPartnership Project (3GPP), although it is emphasized that the presentprinciples described herein may also be applicable to other networktypes and protocols. The environment 100 includes an enterprise 105 inwhich a small cell RAN 110 is implemented. The small cell RAN 110includes a plurality of radio nodes 115 _(1 . . . N). Each radio node115 has a radio coverage area (graphically depicted in the drawings as ahexagonal shape) that is commonly termed a small cell. Thus, the smallcell RAN 110 may be viewed as a small cell network, i.e., a portion of aUMTS Terrestrial Radio Access Network (UTRAN) under 3GPP. A small cellmay also be referred to as a femtocell, or using terminology defined by3GPP as a Home NodeB. In the description that follows, the term “cell”typically means the combination of a radio node and its radio coveragearea unless otherwise indicated. A representative cell is indicated byreference numeral 120 in FIG. 1.

The size of the enterprise 105 and the number of cells deployed in thesmall cell RAN 110 may vary. In typical implementations, the enterprise105 can be from 50,000 to 500,000 square feet and encompass multiplefloors and the small cell RAN 110 may support hundreds to thousands ofusers using mobile communication platforms such as mobile phones,smartphones, tablet computing devices, and the like (referred to as“user equipment” (UE) and indicated by reference numerals 125 _(1-N) inFIG. 1). However, the foregoing is intended to be illustrative and thesmall cell reselection performance improvement can be typically expectedto be readily scalable either upwards or downwards as the needs of aparticular usage scenario demand.

In this particular illustrative example, the small cell RAN 110 includesone or more services nodes (represented as a single services node 130 inFIG. 1) that manage and control the radio nodes 115. In alternativeimplementations, the management and control functionality may beincorporated into a radio node, distributed among nodes, or implementedremotely (i.e., using infrastructure external to the small cell RAN110). The radio nodes 115 are coupled to the services node 130 over adirect or local area network (LAN) connection (not shown in FIG. 1)typically using secure IPsec tunnels. The services node 130 aggregatesvoice and data traffic from the radio nodes 115 and providesconnectivity over an IPsec tunnel to a gateway 135 in a core network 140of a mobile operator. The core network 140 is typically configured tocommunicate with a public switched telephone network (PSTN) 145 to carrycircuit-switched traffic, as well as for communicating with apacket-switched network such as the Internet 150.

The environment 100 also generally includes UTMS Node B base stations,or “macrocells”, as part of the UTRAN as representatively indicated byreference numeral 155 in FIG. 1. The radio coverage area of themacrocell 155 is typically much larger than that of a small cell wherethe extent of coverage often depends on the base station configurationand surrounding geography. Thus, a given UE 125 may achieve UTRANconnectivity through either a macrocell or small cell in environment100.

A UE 125 connected to the UMTS network environment 100 will actively orpassively monitor a UTRAN cell. As shown in FIG. 2, such a cell istermed the “serving cell” 205 and as the UE 125 moves throughout theenvironment 100, it will continually evaluate the quality of the servingcell as compared with that of neighboring cells 210. As shown, bothsmall cells and macrocells can identify themselves to the UE 125 using aunique primary scrambling code (PSC) 215 that is transmitted over adownlink to a UE as representatively indicated by reference numeral 220.By using different PSCs, neighboring cells 210 may thus be disambiguatedfrom the serving cell 205.

There are two different ways in the UMTS network environment 100(FIG. 1) in which the serving cell may be changed. For a UE in activecommunications, called the Cell DCH state using 3GPP terminology, theserving cell changes are controlled by the network using a processtermed “handover.” As shown in FIG. 3, handover between small cells 120in the small cell RAN 110 is supported in a UMTS network to provide RANservice to the UE (RAN service may also utilize reselection in somecases). However, handover between a macrocell and a small cell istypically unsupported in many UMTS deployments. Instead, for UEs 125that are inactive or passively communicating with the network, the UEsautonomously select a new serving cell, through a process called“reselection.” While the reselection process is autonomous, it issteered based on parameters broadcast by the current serving cell. Theseparameters are signaled on the BCH (broadcast channel under 3GPP)channel and indicate the neighboring cell PSCs and signal quality atwhich reselection is permitted.

Accordingly, reselection is typically the only path over which UEs 125can detect the small cell RAN 110 and switch over from the macrocell 155to a small cell 120, as shown in FIG. 4. There are several usagescenarios in which a user would need to reselect to the small cell RAN110. These include, for example:

-   -   1. Ingress: This is a dominant scenario in which a user in the        exterior of the small cell RAN moves into the small cell RAN.    -   2. Redirect: In the case of overload, the small cell RAN        redirects users to the macrocell. This affects UEs not just when        establishing voice traffic, but also UEs handling background        packet-switched traffic. Typically, it can be expected that the        macrocell coverage would be marginal, but once on the macrocell,        the UE will not return to the small cell RAN except through the        reselection procedure. A given small cell RAN may also have        adequate capacity for voice, but if under-dimensioned for        packet-switched traffic, may still bleed users to the macrocell,        and those users would continue to remain on the macrocell when        establishing voice calls.    -   3. Coverage holes: The coverage from the small cell RAN may not        be consistent. For example, laboratories, elevators, atriums,        and other locations in the enterprise may have localized        coverage issues that result in loss of users to the macrocell.    -   4. System issues: Radio system reboots, loss of core network        connectivity, etc., could result in affected users reselecting        to the macrocell.

If reselection performance is not satisfactory, the small cell RAN willsee lower than desired utilization, resulting in continued overload onthe macrocell network and poorer user experience in-building.

Typically, the macrocells in the UMTS network usually reserve a smallset of PSCs for permitting reselection by UEs 125 to the small cell RAN110 (FIG. 1). The PSCs are colloquially known as “magic PSCs” becausethey have special properties—the UE 125 will reselect to a cell 120 inthe small cell RAN 110 identified by a magic PSC even at low “quality”levels, for example, very low RSCP (received signal code power) and SNR(signal-to-noise ratio) levels, thereby accelerating the reselection ofthe UE to cells using these magic PSCs. A representative magic PSC 405is shown in FIG. 4.

Conversely, while some cells 120 in the small cell RAN 110 can useregular (i.e., non-magic PSCs), a UE 125 on the macrocell 155 will neverreselect to a small cell RAN cell 120 that uses a non-magic PSC,regardless of the quality of the non-magic PSC. However, once on thesmall cell RAN 110, the UEs 125 may handover or reselect to a cellhaving any PSC, including non-magic PSC. Since it is typically desirableto redirect users to the small cell RAN as soon as they enter thecoverage area of the small cell RAN for the reasons discussed above,small cells identified by a magic PSC are often located at points withinthe enterprise 105 where such cells can influence the reselection fromthe macrocell 155 for the largest fraction of users.

In typical current implementations of small cell networks (i.e., thosenot utilizing the present small cell reselection performanceimprovement), the configuration of cells having magic PSCs within thesmall cell RAN often needs to be carefully implemented because thequality of magic PSC assignments determines the reselection-inperformance for the small cell RAN. The configuration process typicallyentails two steps. The first step comprises manual configuration ofthose cells using magic PSCs by setting an appropriate parameter in theradio node. As noted above, cells at the ingress routes to the smallcell RAN (e.g., entrances to the enterprise) and cells in common areas(lobbies, atriums, cafeterias, etc.) are recommended as prime candidatesto improve the overall system reselection performance. The second stepcomprises a REM (radio environment measurement) scan and PSC assignment.This is an automated process that generally determines the best PSC tobe used by a cell based on RF and topology considerations.

While the configuration steps discussed above can provide satisfactoryresults in many network implementations, the manual configuration canoften increase the complexity of the installation since it requiresknowledge of the building floor plans, adds additional installation andconfiguration steps, and may be prone to errors. More particularly,insufficient allocation of magic PSCs can result in UEs remaining on themacrocell which has degraded even though they are in the coverage areaof the small cell RAN. In addition, a dense allocation of magic PSCs canresult in disambiguation failures, which, while improving reselectionbehavior, would degrade handover performance.

Such issues may be addressed by a beacon cell that is arranged toimprove reselection performance in small cell systems such as the smallcell RAN 110 shown in FIG. 1 and described in the accompanying text. Asshown in FIG. 5, a beacon cell 505 includes a radio node 510 that isspecially configured to have two distinct identities. One identity is abeacon identity in which the beacon cell 505 can function and behave asa beacon that is specifically intended to capture UEs from the macrocellvia reselection using a magic PSC. The other identity is the standard or“live” identity in which the beacon cell 505 can function and behaveconventionally as a regular small cell to provide RAN service to a UEonce it is associated with the small cell RAN. In some usage scenarios,the beacon cell 505 supports both identities simultaneously, while inother scenarios the beacon identity is utilized on a selective basis, asdescribed in more detail below. Beacon cells may be used to supplementcells that are identified with magic PSCs in a given small cell RANdeployment, or replace such magic PSC cells in their entirety in somecases. Similarly, beacon cells can be used to supplement regular cellsin a given small cell RAN deployment, or replace such cells in somecases.

The configuration of the beacon cell 505 with dual identities results,at least in part, from the recognition that RAN service and reselectionfrom a macrocell have differing performance requirements. Reselectionfrom a macrocell requires a magic PSC but does not rely on celldisambiguation. Additionally, as long as the broadcast channels aredecodable, the overall quality of the cell is not important. Bycontrast, after the UE becomes associated with the small cell RAN viathe beacon identity, the provision of RAN service does not require amagic PSC, but does require cell disambiguation.

Accordingly, in view of the foregoing recognition, the beacon identity520 may include a number of features and characteristics, as shown inFIG. 5. The beacon identity 520 utilizes one or more magic PSCs (asindicated by reference numeral 525). In some cases, the same particularmagic PSC (e.g., one of six reserved PSCs in one illustrativeimplementation scenario) is reused by each of the beacon cells 505 in asmall cell RAN, while in other cases, two, three, or up to all six ofthe magic PSCs are utilized in the beacon cells with varying degrees ofreuse (530). For example, three magic PSCs may be reused across multiplebeacon cells, while two magic PSCs are utilized in single instances, andthe sixth magic PSC is not utilized in a beacon cell and reserved forother uses. Note, however, that it may be desirable in someimplementations to maintain backwards compatibility by reusing a singlemagic PSC for beacon cells while reserving the remaining five magic PSCsfor conventional usage. In the event that handover from a macrocell to asmall cell RAN is supported in the future, some live identities can beconfigured with magic PSCs that are not used by any beacon identities inorder to also provide a path of handover from macrocells to the smallcell RAN. In most typical small cell RAN implementations, once a magicPSC is selected for beacon cell use it should not be configured for useby any other non-beacon cells.

The live identity 515, by comparison to the beacon identity 520, usesregular, non-magic PSCs (as indicated by reference numeral 535). Eachlive identity in a beacon cell uses a spatially unique PSC and PSC reuseis carefully managed (540). For example, in some implementations, it maybe desirable to reuse PSCs for the live identities as infrequently aspossible.

In order to reduce interference between the beacon and live identitieswhen both identities are simultaneously utilized, channel powers cantypically become critically important. Accordingly, the beacon identity520, in comparison to the live identity 515 which broadcastsconventionally, uses a modified broadcast (550) where such modificationscan be described in terms of differences in the SIBs (System InformationBlocks) between the beacon identity and live identity. FIG. 6 shows anillustrative taxonomy 600 of modifications (as indicated by referencenumeral 602) that may be made to several physical and transport channelsin the downlink between the beacon cell and a UE to enable suchbroadcast to minimum requirements for reselection. Such enablemententails configuring certain physical channels to cumulatively utilize nogreater than approximately 20% of regular live cell power (604). Thereconfigured physical channels include PSCH (Primary SynchronizationChannel), SSCH (Secondary Synchronization Channel), CPICH (Common PilotChannel), and PCCPCH (Primary Common Control Physical Channel), asrespectively indicated by reference numerals 606, 608, 610, and 612.

The BCH (Broadcast Channel) may also be configured to aid rapidreselection and prevent a UE from transmitting to the beacon cell athigh power (614). In particular, certain SIBs can be modified: SIB3(616) may be modified to contain a dummy cell ID (618). It may bepossible to reuse the same dummy cell ID for all beacon identitiesacross cells in a given small cell RAN deployment. SIB3 may be furtherconfigured to contain low values for intrafrequency searching, shorttimers, and low reselection hysteresis (620).

SIB5 (622) may be configured to contain a relatively low value for RACH(Random Access Channel) maximum transmit power (624), a relatively largebackoff for RACH retransmits (626), and fewer RACH reattempts (628).SIB5 may be optionally configured, in some implementations, to contain adummy configuration for SCCPCH (Secondary Common Control PhysicalChannel) (630).

SIB11 (632) may be configured to contain only one neighboring cell viathe PSC of a live cell in the neighbor list having large (negative)offsets (634). SIB2 (638) may be dropped as non-essential (640). Each ofthe SIBs (642) may be optionally configured to fit into a repetitioncycle of 16 (i.e., 160 ms) to further expedite the reselection processby reducing the time required for SIB inspection (644).

Returning again to FIG. 5, as noted above, the beacon identity 520 canpresent interference with the live identity 515 which can limit thetotal power available to the cell's normal operation and thuspotentially have some nominal impact on cell capacity in some cases.Typically, the BCH can be decoded by a UE as low as −17 dB chip SNR.Accordingly, the beacon identity 520 can be configured about 5 dB lowerthan the live identity 515 and thus the power utilization of the beaconidentity can be lowered to approximately 6% of the total cell power (asindicated by reference numeral 555). Various control schemes may also beimplemented to allow for dynamic power management of the beacon identity520, for example, using a new control or by a tie-in (560) to anexisting control system or sub-system incorporated in the radio node orexternal to the node, for example, the downlink power manager or HSDPA(High-Speed Downlink Packet Access) power harvesting module. Under suchcontrol, the beacon identity may be powered up and down in anopportunistic manner.

In another illustrative example, in a completely unloaded small cell RANthe CPICH of the beacon identity can have substantially the same powerlevel as the live identity CPICH so as to have the same footprint forboth reselection and normal RAN service operation. In this case, when aUE moves within the small cell RAN, there will be a possibility of itreselecting briefly to the beacon identity of an adjoining beacon cell,which should be avoided when possible. To this end, all beacon cells ina small cell RAN may advertise a magic PSC in their neighbor list inSIB11 with a relatively large hysteresis. This can be expected toprevent such a reselection to the adjoining beacon identity once the UEis within the small cell RAN in many scenarios. It is also possible thatthe reselection to the adjoining beacon identity may even be preventedin cases when the UE goes into a coverage hole and returns back to thesmall cell RAN after going to the macrocell or through a full scan ofall PSCs.

A nominal timing offset of a few chips between the beacon and liveidentities may also be utilized to compensate for the observation thatsome UEs may have difficulty detecting the lower power beacon signalhaving the same timing as a stronger signal from the live identity(565).

The beacon identity 520 may further be optionally configured to beselectively operated (570). That is, the beacon cell 505 can have boththe beacon and live identities operating simultaneously, or the beaconidentity can be selectively switched off so that the beacon cell 505essentially defaults to conventional live cell behavior with no supportfor reselection in from the macrocell. Such selective operation could beimplemented, for example, using a duty cycle methodology or via couplingto a control that has awareness of external conditions such as UEloading on the small cell RAN, or throughput requirements of usersattached to the live identity of the small cell.

Other optional configurations may include enabling an AICH (AcquisitionIndicator Channel) and sending NACKs (non-acknowledgements) on the AICHto prevent UEs from attempting to PRACH (physical random access channel)on the beacon identity, and enabling an SCCPCH (Secondary Common ControlPhysical Channel) and using RRC (Radio Resource Control) reject messagesto influence UE behavior.

FIG. 7 is a flowchart of an illustrative method 700 for improvedreselection performance using multiple instances of the beacon cell 505shown in FIG. 5 and described in the accompanying text when deployed ina small cell RAN. It should be understood that the specific order orhierarchy of the steps in the method disclosed is an illustration ofexemplary approaches. Based upon design preferences, it is understoodthat the specific order or hierarchy of steps in the method may berearranged. The accompanying method claims present elements of thevarious steps in a sample order, and are not meant to be limited to thespecific order or hierarchy presented. The method starts at block 705. AUE is in an inactive state on a macrocell at block 710. At block 715,the UE reads SIBs from the macrocell to get the PSCs of the neighboringcells for reselection. As discussed above, magic PSCs are utilized bycells that support reselection. When the UE moves into small cell RANcoverage, at block 720, it will discover a beacon cell, at block 725.

If the UE can decode the beacon identity SIBs at decision block 730,then control passes to block 735 and the UE will reselect the liveidentity virtually immediately. If the UE cannot decode the beacon cellSIBs for any reason, the UE will continue to stay on the macrocell andcontrol passes back to block 725 and the UE will discover another beaconcell and the above steps are repeated until a live identity in a beaconcell is successfully reselected. Because utilization of beacon cellstypically enables a reselection beacon to be broadcast over a relativelylarge area from many or all of the cells in the small cell RAN, captureof UEs from the macrocell to the small cell RAN is significantlyenhanced. And any UEs that leak out to the macrocell can typically beexpected to be quickly re-acquired by the beacon cell-equipped smallcell RAN.

When a live identity is successfully reselected, then the UE will campon that beacon cell and the small cell RAN will behave and operate asnormal, as shown at block 740. For example, the UE will move from aserving cell to a neighboring cell in the small cell RAN using normalhandover. In some cases, even when the UE is in the coverage area of thesmall cell RAN, it may still not be associated with the small cell RANand additional occurrences of reselection from the macrocell to thesmall cell RAN may need to occur. For example, as discussed above,reselection may be needed subsequent to a UE being directed to amacrocell due to a coverage hole, overload, system error/reboot, or thelike. In such cases, control is returned from decision block 745 back toblock 725, and the method shown in blocks 725-745 is repeated.

FIG. 8 illustratively shows how a small cell RAN 800 may include cellsselected from different cell types. The cell types include: (1) beaconcells 505; (2) non-beacon cells which are identified using a magic PSC,termed “magic PSC cells” here and indicated by reference numeral 805 inFIG. 8, (3) regular, non-beacon cells which are identified using regularPSCs (i.e., non-magic PSCs), termed “regular cells” here and indicatedby reference numeral 810, and (4) a small cell that has a beaconidentity only and no live identity, as indicated by reference numeral815. It is noted that all cell types could be designed and constructed,in some implementations, to share a single common physical platform butdiffer in beacon functionality according to variable configurationsettings. In some cases, such settings may be selectable via executablesoftware on the cell or remote control (e.g., from the services node 130shown in FIG. 1, or at a location that is remote from the small cellRAN), or selected via firmware and/or hardware, or various combinationsof software, firmware, and hardware.

In one illustrative deployment scenario using mixed cell types, thebeacon cells 505 are arranged to commonly share a single magic PSC thusenabling the maximum number of discrete magic PSC cells 805 to also beutilized in the small cell RAN 800. In this scenario, the magic PSCcells are configured and deployed using conventional manual techniques.No regular cells 810 are utilized as all of the cells in the small cellRAN 800, other than the magic PSC cells, are configured as beacon cells505.

In a second illustrative deployment scenario using mixed cell types,beacon cells 505 and magic PSC cells 805 are configured and deployed ina small cell RAN in a similar manner as in the first scenario. Regularcells 810 are also utilized in certain locations in the enterprise wherereselection to the small cell RAN from the macrocell may be undesired(for example, when a cell bleeds out beyond its desired coverage areaover a pedestrian walkway).

In a third illustrative deployment scenario using mixed cell types, thecell 815with beacon identity only can be used to overlay an existingsmall cell RAN deployment of regular cells 810 and magic PSC cells505.The foregoing deployment scenarios are intended to be illustrativeand deployment scenarios using other combinations of cell types andconfigurations are envisioned as required to meet the needs of a givenimplementation.

FIG. 9 shows an illustrative radio interface protocol architecture 900that is arranged in accordance with 3GPP TS 25.201 and which may be usedto facilitate implementation of various aspects of the present beaconcell (e.g., beacon cell 505 in FIG. 5). The architecture 900 is arrangedin three protocol layers: the physical layer (L1) as indicated byreference numeral 905; the data link layer (L2) 910; and the networklayer (L3) 915. The L2 layer 910 above the L1 layer 905 is responsiblefor the link between the UEs and beacon cells over the L1 layer. In theuser plane 920, the L2 layer 910 includes a media access control (MAC)sublayer 925, a radio link control (RLC) sublayer 930, and a packet dataconvergence protocol (PDCP) sublayer 935, which are terminated at thebeacon cell on the network side.

The PDCP sublayer 935 provides header compression for upper layer datapackets to reduce radio transmission overhead and handover support forUEs between small cells. The RLC sublayer 930 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ). The MACsublayer 925 provides multiplexing between logical and transportchannels. The MAC sublayer 925 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 925 is also responsible for HARQ operations.

In the control plane 940, the radio interface protocol architecture 900is substantially the same for the physical layer 905 and the L2 layer910 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 945 in the L3 layer 915. The RRC sublayer 945 isresponsible for obtaining radio resources (i.e., radio bearers) and forconfiguring the lower layers using RRC signaling between the beacon celland the UE.

FIG. 10 shows a simplified functional block diagram of illustrativehardware infrastructure for a radio node (e.g., radio node 510 in FIG.5) that may be utilized to implement the present beacon cell 505. It isemphasized at the outset that the various discrete elements shown areintended to be illustrative, and that functionalities provided by agiven element may be combined with those provided by another element,for example, as a matter of design preference. In addition, someelements are not shown in FIG. 10 for sake of clarity in exposition suchas buses and various circuits such as timing sources, peripherals,analog-to-digital and digital-to-analog converters, voltage regulators,and power management circuits, and the like which are well known in theart, and therefore, will not be described any further.

A controller/processor 1005 implements the functionality of the L2 layer910 shown in FIG. 9 and described in the accompanying text. Thecontroller/processor 1005 may include one or more sub-processors 1010 orcores that are configured to handle specific tasks or functions. Thecontroller/processor 1005 typically provides header compression,ciphering, packet segmentation and reordering, multiplexing betweenlogical and transport channels, and radio resource allocations to the UEbased on various priority metrics. The controller/processor 1005 is alsoresponsible for HARQ operations, retransmission of lost packets, andsignaling to the UE.

An RF processor 1015 implements various signal processing functions forthe downlink including the L1 layer 905 (i.e., physical layer) shown inFIG. 9 and described in the accompanying text. The RF processor 1015 mayinclude one or more sub-processors 1020 or cores that are configured tohandle specific tasks or functions. Exemplary signal processingfunctions include coding and interleaving to facilitate forward errorcorrection (FEC) at the UE and mapping to signal constellations based onvarious modulation schemes (e.g., binary phase-shift keying (BPSK),quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), andM-quadrature amplitude modulation (M-QAM)). The coded and modulatedsymbols are then split into parallel streams. Each stream is then mappedto an OFDM (orthogonal frequency-division multiplexing) subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially pre-coded toproduce multiple spatial streams. Channel estimates from a channelestimator (not shown) may be used to determine the coding and modulationscheme, as well as for spatial processing. The channel estimate may bederived from a reference signal and/or channel condition feedbacktransmitted by the UE. Each spatial stream is then provided to anantenna via a transmitter that modulates an RF carrier with a respectivespatial stream for transmission.

A memory 1025 stores computer-readable code 1030 that is executable byone or more processors in the beacon cell 505 including thecontroller/processor 1005 and/or the RF processor 1015. The memory 1025may also include various data sources and data sinks (collectivelyrepresented by element 1035) that may provide additionalfunctionalities. For example, a data sink may be used to facilitate L3layer processing to the extent that such upper layer processing isimplemented on the beacon cell.

The code 1030 in typical deployments is arranged to be executed by theone or more processors to implement the beacon identity features shownin FIG. 5, including power utilization, timing offsets, and selectiveoperations, as well as the modifications to the transport and physicalchannels shown in FIG. 6 via control of the L1 and/or L2 layers(elements 905 and 910 respectively in FIG. 9). The code 1030additionally enables implementation of both the beacon cell identity andlive identity using the same hardware infrastructure in a given beaconcell when executed.

The hardware infrastructure may also include various interfaces (I/Fs)including a communication I/F 1040 which may be used, for example, toimplement a link to the services node 130 (FIG. 1), LAN, or to anexternal processor, control, or data source. In some cases, a user I/F1045 may be utilized to provide various indications such as power statusor to enable some local control of features or settings.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods described in the foregoingdetailed description and illustrated in the accompanying drawing byvarious blocks, modules, components, circuits, steps, processes,algorithms, etc. (collectively referred to as “elements”). Theseelements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system. By wayof example, an element, or any portion of an element, or any combinationof elements may be implemented with a “processing system” that includesone or more processors. Examples of processors include microprocessors,microcontrollers, digital signal processors (DSPs), field programmablegate arrays (FPGAs), programmable logic devices (PLDs), state machines,gated logic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionalities described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software modules, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise. The software may reside on acomputer-readable media. Computer-readable media may include, by way ofexample, a magnetic storage device (e.g., hard disk, floppy disk,magnetic strip), an optical disk (e.g., compact disk (CD), digitalversatile disk (DVD)), a smart card, a flash memory device (e.g., card,stick, key drive), random access memory (RAM), read only memory (ROM),programmable ROM (PROM), erasable PROM (EPROM), electrically erasablePROM (EEPROM), a register, a removable disk, and any other suitablemedia for storing or transmitting software. The computer-readable mediamay be resident in the processing system, external to the processingsystem, or distributed across multiple entities including the processingsystem. Computer-readable media may be embodied in a computer-programproduct. By way of example, a computer-program product may include oneor more computer-readable media in packaging materials. Those skilled inthe art will recognize how best to implement the described functionalitypresented throughout this disclosure depending on the particularapplication and the overall design constraints imposed on the overallsystem.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A method for configuring a small cell in a small cell radio accessnetwork (RAN), the method comprising the steps of: configuring a firstidentity in the small cell for accommodating conventional user equipment(UE) behavior, the conventional UE behavior including reselection in tothe small cell network from a cell on another RAN, the other RAN notbeing managed by the small cell RAN; configuring a second identity inthe small cell for providing a RAN service, the RAN service facilitatingservice to the UE within the small cell RAN; and optimallyre-associating the UE between the first and second identities of thesmall cell.
 2. The method of claim 1 in which the RAN service isimplemented using reselection.
 3. The method of claim 1 in which the RANservice is implemented using handover.
 4. The method of claim 1 in whichthe first identity is a beacon identity and including a further step ofdynamically managing a power level of the beacon identity.
 5. The methodof claim 4 in which the dynamic management is implemented, at least inpart, via a coupling to a control system or sub-system, the controlsystem or sub-system being incorporated into small cell or beingexternal to the small cell.
 6. The method of claim 1 in which the firstidentity is a beacon identity and the second identity is a live identityand including a further step of operating the beacon identity and liveidentity to have substantially similar power levels.
 7. The method ofclaim 1 including a further step of broadcasting a magic PSC in a smallcell's neighbor list in SIB11 (System Information Block 11) with arelatively large hysteresis.